This proposal is based on our recent imaging studies in children that show our ability to image functional and anatomical changes in a pediatric model of Complex Regional Pain Syndrome (CRPS). CRPS may develop following relatively minor trauma to the limbs. Patients typically present with limb pain and stiffness, hypersensitivity, and functional loss. Unlike adult CRPS, however, pediatric CRPS will usually resolve completely and thus provides a unique model of chronic pain reversal. Our preliminary findings suggest that even minor trauma to a limb may result in significant neural (i.e., structural and functional) changes in the pediatric brain over time, persisting well into and beyond the recovery period. This may well be a distinctive feature of pediatric CRPS and serves as a central focus of this investigation. The overarching goal of the research proposed is to determine whether such changes to the pediatric brain are reversible; and if so, what role this biological process may play in elucidating adult CRPS and in developing more effective therapies for both populations. Against this backdrop, we will investigate neural plasticity using imaging techniques in a longitudinal study of pediatric CRPS patients (in pain and in early pain-free states) and in a cross-sectional study of recovered CRPS patients and healthy controls (up to 24 months following symptomatic recovery). The specific aims are (1) To measure the functional (fMRI) changes in the brains of CRPS patients (ages 14-16) first during the painful state, and then, during the early recovery (within 3 months) state, comparing these changes to those noted in age/gender matched controls; (2) To define plasticity of changes in cortical thickness and white matter tracts (using diffusor tensor imaging - DTI) in pediatric patients ages 14-16 with CRPS affecting their leg during their painful and early recovered states, vs. age/gender matched controls; (3) To measure the same functional (as in Aim 1) and anatomical changes (as in Aim 2) in a cross sectional study of cohorts of recovered CRPS patients at 6, 12 and 24 months following their recovery; we will compare these changes with age- gender matched controls. Each aim will test specific hypotheses related to the functional and anatomical changes that take place in pediatric CRPS population.